Yesterday's Tractor Co.
Shop Now View Cart
   Allis Chalmers Case Farmall IH Ford 9N,2N,8N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   Traditional YT Forum ViewClassic View   RegisterRegister 
 ProfileProfile    Log inLog in 

Lesson on Solenoids


 
Post new topic    
View previous topic :: View next topic  
Author Message
1 Acre Warrior
Regular


Joined: 27 Oct 2019
Posts: 39


Report to Moderator

PostPosted: Sun Dec 08, 2019 10:31 am    Post subject: Lesson on Solenoids Reply to specific post Reply with quote

A lesson on solenoids:

A solenoid is simply a switch, that is operated by an electromagnet. Early vehicles with starters used a heavy-duty switch that was operated by the foot, to carry current from the battery to the starter.

The problems with this system are the longer cable leads needed (battery to switch to starter), and the requirement to keep those leads out of the passenger compartment, which usually meant mounting the switch through the floorboard.

The use of solenoids allows for a low-current switch to be mounted on the dash or as part of the ignition key switch, and the heavy cable needed goes straight from battery to starter solenoid, then another from solenoid to starter.

The solenoid must have at least three terminals. Two of these are big, for the cables. They are "normally open," disconnected from each other. Inside the solenoid, there is an electromagnet, a spring-loaded metal piston and some means of closing the connection between the two big contacts (usually a large metal disk).

Apply current to the third terminal, and the electromagnet energizes and pulls the piston until contact is made between the big contacts ("closed" position). Current flows between them.

Every time the solenoid operates with the battery and started connected, an arc passes between each contact and the moving disk. Eventually, there is enough arcing that the contacts burn or wear, and no longer pass enough current to turn the starter.

If convenient, simply replace it with a similar solenoid. If desired, a solenoid can often be fixed by opening it up and cleaning all of the contacts. WARNING : The return spring inside the solenoid is STRONG. The use of a vise or other device to remove spring compression in a controlled manner is necessary!

Solenoids are rated by VOLTAGE and CURRENT. There are actually two different volt/amp ratings for a solenoid. One is for "pull-in" (the electromagnet), which may require 12V at 2A to fully operate.

When you hear the familiar "clack-clack-clack-clack" from a low battery, you're getting enough to pull in, but the heavy load from the starter is dropping voltage too low to hold the starter, so it releases. Once the load drops, there is enough voltage to pull in the solenoid again, with another "clack." A single clack which doesn't release until you release the key may mean that contact is not being made between the big terminals. Check this with voltmeter or test light.

If contact is not being made, repeatedly hitting the starter switch may either clean the contacts enough to operate or allow the internal disk to rotate far enough to reach a good contact point. If this works, consider yourself lucky and replace or repair the solenoid ASAP, before it fails completely.

The other rating is for the switch itself, which may be hundreds or even thousands of volts and/or amps. So long as it is higher than the load (in this case, from the starter and any accessories), it will work. Any 12V, 400A solenoid will do the job of any other with the same rating, EXCEPT that some solenoids have three terminals and some have one or more additional small terminals, which may be used to provide a ground, or toggle such things as electrical accessories, lights, etc. Any of these can be adapted to the three-lead electrical system by simply finding the terminal which runs to the starter switch, and finding the necessary ground connection. Insulate the unnecessary terminals.

Solenoids are NOT polarity-dependent. The electromagnet will pull in the same way whether positive- or negative-grounded.

A solenoid can be bypassed simply by making contact between the two large terminals with a metal object which is heavy-duty enough to withstand the current. It should be kept in mind that it is not the (low) voltage which does the work in an arc welder, it's the (high) current, and select your bypass accordingly, and WEAR EYE PROTECTION.
 
Back to top
View user's profile
JMOR
Tractor Guru


Joined: 13 Aug 2007
Posts: 25790


Report to Moderator

PostPosted: Sun Dec 08, 2019 2:21 pm    Post subject: Re: Lesson on Solenoids Reply to specific post Reply with quote

1 Acre Warrior wrote:
(quoted from post at 14:31:06 12/08/19) A lesson on solenoids:

A solenoid is simply a switch, that is operated by an electromagnet. Early vehicles with starters used a heavy-duty switch that was operated by the foot, to carry current from the battery to the starter.

The problems with this system are the longer cable leads needed (battery to switch to starter), and the requirement to keep those leads out of the passenger compartment, which usually meant mounting the switch through the floorboard.

The use of solenoids allows for a low-current switch to be mounted on the dash or as part of the ignition key switch, and the heavy cable needed goes straight from battery to starter solenoid, then another from solenoid to starter.

The solenoid must have at least three terminals. Two of these are big, for the cables. They are "normally open," disconnected from each other. Inside the solenoid, there is an electromagnet, a spring-loaded metal piston and some means of closing the connection between the two big contacts (usually a large metal disk).

Apply current to the third terminal, and the electromagnet energizes and pulls the piston until contact is made between the big contacts ("closed" position). Current flows between them.

Every time the solenoid operates with the battery and started connected, an arc passes between each contact and the moving disk. Eventually, there is enough arcing that the contacts burn or wear, and no longer pass enough current to turn the starter.

If convenient, simply replace it with a similar solenoid. If desired, a solenoid can often be fixed by opening it up and cleaning all of the contacts. WARNING : The return spring inside the solenoid is STRONG. The use of a vise or other device to remove spring compression in a controlled manner is necessary!

Solenoids are rated by VOLTAGE and CURRENT. There are actually two different volt/amp ratings for a solenoid. One is for "pull-in" (the electromagnet), which may require 12V at 2A to fully operate.

When you hear the familiar "clack-clack-clack-clack" from a low battery, you're getting enough to pull in, but the heavy load from the starter is dropping voltage too low to hold the starter, so it releases. Once the load drops, there is enough voltage to pull in the solenoid again, with another "clack." A single clack which doesn't release until you release the key may mean that contact is not being made between the big terminals. Check this with voltmeter or test light.

If contact is not being made, repeatedly hitting the starter switch may either clean the contacts enough to operate or allow the internal disk to rotate far enough to reach a good contact point. If this works, consider yourself lucky and replace or repair the solenoid ASAP, before it fails completely.

The other rating is for the switch itself, which may be hundreds or even thousands of volts and/or amps. So long as it is higher than the load (in this case, from the starter and any accessories), it will work. Any 12V, 400A solenoid will do the job of any other with the same rating, EXCEPT that some solenoids have three terminals and some have one or more additional small terminals, which may be used to provide a ground, or toggle such things as electrical accessories, lights, etc. Any of these can be adapted to the three-lead electrical system by simply finding the terminal which runs to the starter switch, and finding the necessary ground connection. Insulate the unnecessary terminals.

Solenoids are NOT polarity-dependent. The electromagnet will pull in the same way whether positive- or negative-grounded.

A solenoid can be bypassed simply by making contact between the two large terminals with a metal object which is heavy-duty enough to withstand the current. It should be kept in mind that it is not the (low) voltage which does the work in an arc welder, it's the (high) current, and select your bypass accordingly, and WEAR EYE PROTECTION.
Right about where you said, "Any of these can be adapted to the three-lead electrical system by simply finding the terminal which runs to the starter switch, and finding the necessary ground connection.", you can add that some require voltage to be applied to the small activating terminal and others require grounding that terminal in order to activate.
 
Back to top
View user's profile
Colin King
Tractor Guru


Joined: 16 Oct 2001
Posts: 4519
Location: Clotho, MN

Report to Moderator

PostPosted: Sun Dec 08, 2019 5:46 pm    Post subject: Re: Lesson on Solenoids Reply to specific post Reply with quote

Excellent post!
 
Back to top
View user's profile Visit poster's website
oldsarge
Tractor Expert


Joined: 02 Jul 2014
Posts: 1883


Report to Moderator

PostPosted: Sun Dec 08, 2019 9:05 pm    Post subject: Re: Lesson on Solenoids Reply to specific post Reply with quote

Couldn't have said it better myself
 
Back to top
View user's profile
Biffer5
Regular


Joined: 12 Dec 2016
Posts: 73


Report to Moderator

PostPosted: Mon Dec 09, 2019 5:59 am    Post subject: Re: Lesson on Solenoids Reply to specific post Reply with quote


Thanks. Very helpful to us dumb asses that never really knew what the solenoid was for....
 
Back to top
View user's profile
jimtrs
Regular


Joined: 19 Feb 2008
Posts: 269
Location: Sandown, NH

Report to Moderator

PostPosted: Mon Dec 09, 2019 11:05 am    Post subject: Re: Lesson on Solenoids Reply to specific post Reply with quote

Great write up. Not to get picky but ....

What you say is correct for a "Starter Relay", often referred to (incorrectly so) as a solenoid.

A solenoid operates in a similar fashion as a starter relay, but is wired different internally and usually moves something externally, like a starter drive or pinion to engage with a flywheel.


ALSO ....

There are other flavors of starter relays. Some are internally live, and require external grounding to complete the circuit (think 8n's). Some are internally grounded (through the mounting of relay), and require voltage to complete the circuit (think most other starter relay applications, snow plow relays, etc).

Then there is the "4th" terminal relay marked "I" or "R". This provides current only while the relay is energized (cranking the starter). This usually provides full current to the ignition coil while cranking. Also used sometimes to power fuel pumps during starting.
 
Back to top
View user's profile
:   
Post new topic    Yesterday's Tractors Forum Index -> Ford 9N, 2N, 8N All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  

TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

YT Home  |  Forums

Modern View Forum powered by phpBB © 2001, 2005 phpBB Group

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters